Small-form-factor fiber optic interface devices with an internal lens

ABSTRACT

Small-form-factor fiber optic interface devices with an internal lens are disclosed. The fiber optic interface devices have a ferrule with a bore that supports an optical waveguide. The lens is on or adjacent the ferrule front end and is aligned with the bore. A first planar surface is provided on or adjacent the lens. The first planar surface interfaces with a second planar surface of a second fiber optic interface device to form a fiber optic interface assembly having a liquid-displacing interface when the first and second fiber optic interface devices are engaged.

CLAIM OF PRIORITY

This application is a divisional of U.S. patent application Ser. No.13/050,010 filed on Mar. 17, 2011, which claims the benefit of priorityunder 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No.61/315,430, filed on Mar. 19, 2010, which application is incorporated byreference herein.

FIELD

The present disclosure relates generally to fiber optic fiber opticinterface devices, and in particular relates to small-form-factor fiberoptic interface devices having an internal lens.

BACKGROUND

Optical fiber is increasingly being used for a variety of applications,including but not limited to broadband voice, video, and datatransmission. As consumer devices are steadily using more bandwidth,connectors for these devices will likely move away from strictlyelectrical connections and toward using optical connections forincreased bandwidth. Generally speaking, conventional fiber opticinterface devices used for telecommunication networks and the like arenot suitable for consumer electronic devices.

For instance, conventional fiber optic interface devices are relativelylarge compared with the consumer electronic devices and theirinterfaces. Additionally, conventional fiber optic interface devices aredeployed with great care into relatively clean environments and/orcleaned by the craft before connecting to the device interface. Further,even though fiber optic interface devices are reconfigurable (i.e.,suitable for mating/unmating), they are not intended for a relativelylarge number of mating cycles. Instead, conventional fiber opticinterface devices are high-precision devices designed for reducinginsertion loss between mating devices in the optical network.

On the other hand, the consumer electronic devices are expected to havea relatively large number of mating/unmating cycles during ordinaryoperation. The consumer electronic devices will be operated in amultitude of environments where contaminants such as dirt, dust, andother debris are encountered on a regular basis. Further, consumerelectronic devices typically have size and space constraints for makingconnections. Consequently, there is an unresolved need for fiber opticinterface devices suitable for consumer electronic devices.

SUMMARY

An aspect of the disclosure is a ferrule assembly for a first fiberoptic interface device for engaging a second fiber optic interfacedevice having a second planar surface. The ferrule assembly includes aferrule having a front end and a bore configured to support an opticalwaveguide. The bore has an end at or adjacent the ferrule front end. Theferrule assembly also includes a lens on or adjacent the ferrule end.The lens is aligned with the bore and is operably arranged relative tothe bore end. The ferrule assembly also includes a first planar surfaceprovided on or adjacent the lens. The first and second planar surfacesdefine a liquid-displacing interface when the first and second fiberoptic interface devices are engaged.

In an example of the above-described ferrule assembly, the lens isdefined by an internal surface of an endcap that fits over the ferrulefront end, with the endcap external surface serving as the first planarsurface. In another example of the above-described ferrule assembly, thelens is defined by an external surface of the endcap, and a transparentmember covers the endcap external surface, with the transparent memberhaving a planar surface that defines the first planar surface. The lensmay also be a gradient index (GRIN) lens that has a front surface thatdefines the first planar surface. In an example, the GRIN lens may be ofthe type formed by ionic diffusion into glass rods, or may be of thetype formed by drawing a pre-form so that it has a select size andrefractive index profile. An example pre-form is an optical fiberpreform used to form gradient-index optical fibers.

Another aspect of the disclosure is a ferrule assembly for a first fiberoptic interface device configured to engage a second fiber opticinterface device having a second planar surface. The ferrule assemblyincludes a ferrule having a front end and a bore configured to supportan optical waveguide. The bore has an end that terminates within theferrule at a distance from the ferrule front end. The assembly alsoincludes a lens having a front convex surface, with the lens alignedwith the bore. The assembly further includes a substantially transparentmember disposed adjacent the convex surface. The substantiallytransparent member has a first planar surface that when interfaced withthe second planar surface defines a liquid-displacing interface when thefirst and second fiber optic interface devices are engaged.

Another aspect of the disclosure is a ferrule assembly for a first fiberoptic interface device configured to engage a second fiber opticinterface device having a second planar surface. The ferrule assemblyincludes a ferrule having a front end, a front section at the front end,and a bore configured to support an optical waveguide. The bore has anend at or adjacent the ferrule front end. The ferrule assembly alsoincludes an endcap configured to fit over the ferrule front section. Theendcap has a front end defined by an endwall that supports a GRIN lenshaving a first planar front surface substantially at the endcap frontend and a rear surface immediately adjacent the ferrule front end. Thefirst and second planar surfaces define a liquid-displacing interfacewhen the first and second fiber optic interface devices are engaged. TheGRIN lens may be of the types as formed by the two different techniquesmentioned above.

Another aspect of the disclosure is a ferrule assembly for a first fiberoptic interface device configured to engage a second fiber opticinterface device having a second planar surface. The ferrule assemblyincludes a ferrule body having a front end that defines a first planarsurface, and an internal cavity having a front surface and a rearsurface. The ferrule has a bore that supports an optical waveguidehaving an end. The bore terminates at a bore end within the ferrule bodyadjacent the internal cavity rear surface. The optical waveguide endresides substantially at the bore end. An example optical waveguide isan optical fiber. The ferrule includes a first cylindrical lens on theinternal cavity front surface and that as optical power in a firstdirection. The ferrule also has a second cylindrical lens on theinternal cavity rear surface that is axially spaced apart from the firstcylindrical lens. The second cylindrical lens has optical power in asecond direction orthogonal to the first direction. The first and secondplanar surfaces define a liquid-displacing interface when the first andsecond fiber optic interface devices are mated.

Another aspect of the disclosure is a method of transmitting lightthrough a liquid-displacing interface. The method includes supporting ina ferrule of a ferrule assembly an optical fiber having an end. Theferrule supports a lens operably arranged relative to the optical fiberend. The ferrule assembly has a front end that defines a first planarfront surface. The method also includes interfacing the first planarfront surface with a second planar front surface of a light-transmittingmember to define the liquid-displacing interface. The method furtherincludes transmitting the light through the optical fiber, through thelens and through the liquid-displacing interface and tolight-transmitting member.

It is to be understood that both the foregoing general description andthe following detailed description present embodiments of thedisclosure, and are intended to provide an overview or framework forunderstanding the nature and character of the disclosure as it isclaimed. The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated into andconstitute part of this specification. The drawings illustrate variousexemplary embodiments of the disclosure, and together with thedescription serve to explain the principles and operations of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front elevated view of an example fiber optic interfacedevice in the form of a plug having a main housing that comprises frontand rear housings;

FIG. 1B is a front elevated view of another example fiber opticinterface device having a single unitary housing;

FIG. 2 is a cross-sectional view of the fiber optic interface device ofFIG. 1A as seen in the Y-Z plane, and including an optical fiber;

FIG. 3 is a close-up cross-sectional view of the front end of the fiberoptic interface device shown in FIG. 2;

FIG. 4A and FIG. 4B are front and rear elevated views of an exampleendcap for a fiber optic interface device;

FIG. 5A and FIG. 5B are cross-sectional views of the example endcap ofFIG. 4A and FIG. 4B;

FIG. 6 is a close-up cross-sectional view of the ferrule assembly forthe fiber optic interface device, illustrating how the internal lens ofthe endcap serves to collimate light from an optical fiber supported inthe ferrule;

FIG. 7A is a top elevated view of the fiber optic interface device shownoperably engaged with an another fiber optic interface device byinterfacing their respective planar surfaces to form a fiber opticinterface assembly;

FIG. 7B is a similar view to FIG. 7A, but with the two fiber opticinterface devices disengaged and showing the respective planar surfaces;

FIG. 7C is a cross-sectional view of the operably engaged fiber opticinterface devices of FIG. 7A;

FIG. 7D is a schematic cross-sectional view of fiber optic interfaceassembly of FIG. 7A, illustrating an example light path from the plugand through the light-transmitting member of the receptacle;

FIG. 7E is another example cross-sectional view of the operably engagedfiber optic interface devices showing more detail of the electronicdevice that houses one of the fiber optic interface devices;

FIG. 8A and FIG. 8B are similar to FIG. 5A and FIG. 5B, and illustrateanother example embodiment of an endcap for fiber optic interfacedevice, where the endcap has a lens formed on the endcap front surface;

FIG. 9A is a cross-sectional view similar to FIG. 6, and shows anexample where the endcap lanes is formed on the endcap front surface,and where a substantially transparent member having a planar surface isused to cover the endcap front end to define the planar interfacesurface;

FIG. 9B is a front-on view of the substantially transparent member asheld by the endcap at the endcap front end;

FIG. 9C is a close-up cross-sectional view of the front end of theendcap showing how the substantially transparent member is held at thefront end by an annular lip;

FIG. 10A is similar to FIG. 9A, and illustrates an example embodiment ofa ferrule assembly for a fiber optic interface device where the endcapincludes a GRIN lens;

FIG. 10B is similar to FIG. 10A, and illustrates an example embodimentwhere the GRIN lens is incorporated directly into the ferrule so that noendcap is need to support the GRIN lens;

FIG. 10C is a cut-away view of an example ferrule for a fiber opticinterface device where the ferrule includes a GRIN lens at the ferruleend, with the ferrule operably engaged with another ferrule that alsoincludes a GRIN lens;

FIG. 10D is similar to FIG. 10B, but with the two ferrules disengaged;

FIG. 11A is a top elevated view of an example ferrule shown operablyengaged to an example light-transmitting member, where the ferruleincludes crossed cylindrical lenses;

FIG. 11B is a similar view but with the plug ferrule shown disengagedfrom the light-transmitting member;

FIG. 11C and FIG. 11D are cut-away views of the mated light-transmittingmember and the ferrule of FIGS. 11A and 11B;

FIG. 12A and FIG. 12B are close-up, cross-sectional views of the ferruleinternal cavity and the optical fiber supported in the ferrule bore,with the cross-section of FIG. 12A taken in the X-Z plane andcross-section of FIG. 12B taken in the Y-Z plane;

FIG. 13A is a top elevated view of an example ferrule having anotherexample configuration of crossed cylindrical lenses, with the ferruleshown operably engaged with a light-transmitting member; and

FIG. 13B is a cut-away view of the engaged ferrule andlight-transmitting member of FIG. 13A, showing the example configurationof the cross-cylindrical lenses.

DETAILED DESCRIPTION

Reference is now made in detail to the present preferred embodiments ofthe disclosure, examples of which are illustrated in the accompanyingdrawings. Whenever possible, like or similar reference numerals are usedthroughout the drawings to refer to like or similar parts. Variousmodifications and alterations may be made to the following exampleswithin the scope of the present disclosure, and aspects of the differentexamples may be mixed in different ways to achieve yet further examples.Accordingly, the true scope of the disclosure is to be understood fromthe entirety of the present disclosure, in view of but not limited tothe embodiments described herein.

In some of the Figures, Cartesian coordinates are shown for reference.Also, the terms “plug” and “receptacle” are used as shorthand terms todistinguish between different types of fiber optic interface devicesthat form part of a fiber optic interface assembly, which is referred tobelow as a “connector assembly.” Further, in some of the examplesdiscussed below, the receptacle is part of an electronic device, and isconfigured to receive a plug.

The term electronic device as used herein means a device that has eitherelectronic or both optical and electronic components and functionality,including a fiber optic interface device and associated hardware (e.g.,an integrated optical engine) that can receive, transmit or bothtransmit and receive optical signals.

FIG. 1A is a front elevated view of an example fiber optic interfacedevice (“plug”) 10. Plug 10 is shown as having a two-part constructionby way of illustration. However, one skilled in the art will appreciatethat other configurations, including various unitary configurations, canbe implemented based on the description set forth herein. A plug 10having a housing 16 with a unitary construction is illustrated in FIG.1B by way of example. The housing 16 of FIG. 1B includes a strain-reliefsection (boot) 28.

FIG. 2 is a cross-sectional view of the plug 10 of FIG. 1A as seen inthe Y-Z plane along with an optical fiber cable 600 that carries atleast one optical fiber 602. Plug 10 and optical fiber cable 600constitute a fiber optic interface assembly 6.

With reference to FIG. 2, plug 10 has a main housing 16 shown ascomprised of a front housing 20 mated with a rear housing 120. Fronthousing 20 has front and rear ends 22 and 24, an outside surface 26 andan interior 50. Front housing 20 includes a narrow rear section 40 atrear end 24. Interior 50 includes a front section 52 that transitions toa narrower mid-section 54 at an interior ledge 56. Interior mid-section54 in turn narrows down to a rear lead-in section 58 associated withnarrow rear section 40.

Rear housing 120 includes front and rear ends 122 and 124, an outersurface 126 and an interior 150. Rear housing interior 150 includes achannel 154 defined in part by a tube section 140 that extends beyondrear housing front end 122 and that has a front end 142. Rear housinginterior 150 also includes an annular slot 156 surrounding tube section140 at rear housing front end 122. Annular slot 156 is configured toreceive narrow rear section 40 of front housing 20, with tube section140 extending through rear lead-in section 58 and into mid-section 54 offront housing 20.

FIG. 3 is a close-up cross-sectional view of the front end of the plug10 as shown in FIG. 2. Front housing 20 includes a plug ferrule holder80 supported within front housing interior 50 at front section 52. Plugferrule holder 80 is configured to support a plug ferrule 200. In otherembodiments, a plug ferrule holder is not employed and front housing 20is configured to hold plug ferrule 200. Plug ferrule 200 in combinationwith one or more additional components is referred to below as a plugferrule assembly.

With reference to FIG. 2 and FIG. 3, plug ferrule 200 includes a ferrulebody 201 having a front end 202 and a rear end 204. Plug ferrule 200 canhave a number of configurations. The example plug ferrule 200 includes acylindrical front section 205 adjacent the front end, a mid-section 210and a generally cylindrical rear section 216 adjacent rear end 204.Mid-section 210 is flared and is configured so that plug ferrule frontsection 205 is narrower than plug ferrule rear section 216. Thetransition from front section 205 to mid-section 210 includes a step 220and the transition from the mid-section 210 to rear section 216 includesfront and rear steps 222 and 223 defined by a ridge 224. Rear section216 defines an open rear interior section 234 open at rear end 204 andextending into the rear section up until an internal endwall 240. Plugferrule 200 includes a central bore 250 having a front end 252 at thefront end 202 of the plug ferrule and a rear end 254 at internal endwall240. In an example, central bore 250 includes a flared portion 260adjacent internal endwall 240.

Front end 142 of tube section 140 of rear housing 120 extends into plugferrule rear interior section 234 and is snugly held therein. Aresilient member 300 having a front end 302 and a rear end 304 isarranged around a portion of plug ferrule rear section 216 and a portionof tube section 140 of rear housing 120. Resilient member 300 is held inplace at its front end 302 by rear step 223 of plug ferrule rear section216 and by ledge 56 that defines the transition between the housinginterior front section 52 and mid-section 54. In an example, resilientmember 300 comprises a cylindrical spring, as shown.

Plug 10 further includes a substantially transparent plug endcap 400configured to fit over front section 205 of plug ferrule 200. Thecombination of the plug endcap 400 and plug ferrule 200 constitutes aplug ferrule assembly 430. FIG. 4A and FIG. 4B are front and rearelevated views of an example plug endcap 400, and FIG. 5A and FIG. 5Bare cross-sectional views of the example plug endcap of FIG. 4A and FIG.4B. Plug endcap 400 has a body 401 with a front end 402 having a frontsurface 403, and an opposite rear end 404. Plug endcap body 401 has aninterior 410 defined by interior sidewall 411. Interior 410 has a frontsection 412 and a rear section 414 open at rear end 404. In an example,front section 412 has a smaller diameter than rear section 414, with thetransition between these interior sections defined by a step 420.Interior 410 includes a longitudinal venting slot 426 formed in interiorsidewall 411 and that extends from rear end 404, through rear interiorsection 414 and part-way into front interior section 412. Venting slot426 serves as a vent that allows air to escape while placing plug endcap400 over front section 205 of plug ferrule 200.

In an example where plug ferrule front section 205 is cylindrical, plugendcap 400 has an interior 410 that is also cylindrical so that the plugendcap can slidingly engage with and cover the plug ferrule frontsection to form plug ferrule assembly 430.

The front section 412 of plug endcap interior 410 is defined in part byan endwall 450 that defines endcap front surface 403 and that alsoincludes an interior surface 462 opposite the front surface. In anexample, interior endwall surface 462 is curved, such as shown in FIGS.5A and 5B. Thus, the planar front surface 403 of plug endcap 400, thecurved surface of interior endwall 462, and the intervening body portion401 of endwall 450 constitute a plug lens 500. In an example, endcap 400is made of a material that is substantially transparent to thewavelength of operation, for example to wavelengths in the range 850±50nm, or 1310±50 nm, or 1550±50 nm, or generally in the range from 800 nmto 1600 nm. Example materials for endcap 400 include Polyetheremide((PEI), sold by the General Electric Company under the trademarked nameULTEM® 1010).

When plug endcap 400 is placed over front section 205 of plug ferrule200 to form plug ferrule assembly 430, plug endcap rear end 204 butts upagainst step 220 at the transition from the plug ferrule front section205 to mid-section 210. This places endcap 400 in the proper positionrelative to plug ferrule 200 and defines a gap 480 between plug ferrulefront surface 203 and endcap endwall 450. In an example, gap 480 has anaxial width that is substantially the same as the focal length of pluglens 500, i.e., the plug lens and plug ferrule front end 202 areseparated by about the focal length of the plug lens.

With reference again to FIG. 3, in an example ferrule 200 and endcap 400include respective keying features KF and KF′ that allow for a selectorientation of the endcap on the ferrule.

With reference again to FIG. 2, optical fiber cable 600 includes ajacketed section 604, a buffered section 610 and a bare optical fibersection 616 that has an end 618. The transition from bare fiber section616 to buffered section 610 includes a transition step 620. Bufferedsection 610 resides within rear housing channel 154 including tubesection 140 so that the transition step 620 contacts plug ferruleinternal endwall 240. Bare fiber section 616 resides in plug ferrulecentral bore 250 so that bare fiber end 618 resides at or close to plugferrule front end 202. Note that flared portion 260 of central bore 250adjacent internal endwall 240 serves to facilitate the insertion of bareoptical fiber section 616 into the central bore.

FIG. 6 is a close-up, cross-sectional view of plug ferrule assembly 430showing the plug endcap 400 in place covering plug ferrule front end202. Bare optical fiber section 616 resides within plug ferrule centralbore 250 so that bare optical fiber section end 618 is in substantiallythe same plane as plug ferrule front end 202. Light 650 traveling inoptical fiber 602 from a light source (not shown) attached to the farend of optical fiber cable 600 reaches bare optical fiber end 618. Light650 diverges as it exits bare optical fiber end 618 and travels acrossgap 480 to lens surface 460. Light 650 refracts at lens surface 460 andbecomes substantially collimated light 650C. Substantially collimatedlight 650C continued to travel through plug lens 500 and exits endcapfront surface 403 as a substantially collimated light beam.

FIG. 7A is a top elevated view of plug 10 shown operably engaged with anexample fiber optic interface device (“receptacle”) 700 to form a fiberoptic interface assembly 470 having a planar-surface to planar-surfaceinterface IF, as described below. FIG. 7B is similar to FIG. 7A, butwith plug 10 shown disengaged from receptacle 700, and showing therespective plug and receptacle planar interface surfaces 403 and 403′.

FIG. 7C is a cross-sectional view of the operably engaged plug 10 andreceptacle 700 of FIG. 7A, and includes a close-up inset view of theinterface surfaces. Receptacle 700 includes a light-transmitting member710. Light-transmitting member has a body 711 with a front end 712having a planar front surface 713. Light-transmitting member 710 has afront section 714 at front end 712. Light-transmitting member body 711also has an angled surface 716 and an input/output end 720 with asurface 721 that is curved to define a convex lens 750.

In an example, light-transmitting member body 711 is made of theaforementioned material ULTEM®, which is transparent at wavelengths from800 nm through 1600 nm. In an example, light-transmitting member 710 isformed as having a unitary body 711, and is configured via molding,machining or both.

Receptacle 700 includes a receptacle endcap 400′ similar to plug endcap400. Receptacle endcap 400′ has a body 401′ having a front end 402′defined by an enwall 450′ having the aforementioned planar front (outer)surface 403′ and an opposite interior surface 462′. The planar frontsurface 403′, the curved surface of interior endwall 462′, and theintervening body portion 401′ of endwall 450′ constitute a receptaclelens 500′ similar to plug lens 500. Receptacle endcap 400′ is configuredto slide over and engage light-transmitting member front section 714 todefine a receptacle light-transmitting assembly 430′ that hasessentially a complementary configuration to plug ferrule assembly 430.

With reference now also to FIG. 7D, plug 10 engages receptacle 700 suchthat the planar surfaces 403 and 403′ of the plug and receptacle endcaps400 and 400′ form interface IF. Divergent light 650D is emitted fromoptical fiber end 618 and is incident upon plug lens 500, which formssubstantially collimated light 650C. This substantially collimated light650 travels out of plug endcap front surface 403 and through receptacleendcap front surface 403′. In an example, receptacle lens 500′ hasrelatively low optical power and serves to slightly convergesubstantially collimated light 650C to form weakly focused light 650F1.This weakly focused light internally reflects from angled surface 716and travels to another receptacle lens 750 on bottom surface 721 ofinput/output end 720. Lens 750 acts to more strongly converge the weaklyfocused light 650F1 to form more strongly focused light 650F2. In anexample, the interfaced planar surfaces 403 and 403′ are made to contacteach other at interface IF.

FIG. 7E is another example cross-sectional view of the mated plug 10 andreceptacle 700 as part of an electronic device 706 that houses thereceptacle. In the embodiment of FIG. 7D, light-transmitting memberfront surface 713 is planar and is used as the interfacing surface.Also, light-transmitting member input/output end 720 is arrangedadjacent a circuit board 740 supported within electronic device 706.Circuit board includes an active device 760 such as a photodetector, ora light-emitting device such as a vertical-cavity surface-emitting laser(VCSEL).

When plug 10 engages receptacle 700, the planar front surface 403 ofplug endcap 400 confronts and interfaces with the planar front surface713 of light-transmitting member 710. This allows for substantiallycollimated light 650C to travel out of the plug endcap front surface 403and through planar front surface 713 of light-transmitting member 710.The substantially collimated light 650C continues to travels throughbody 711 of light-transmitting member 710, where it internally reflectsfrom angled portion 716. This internal reflection directs substantiallycollimated light 650C to input/output end 720 of light transmittingmember 710 and to convex lens 750. Convex lens 750 serves to focussubstantially collimated light 650C, thereby forming strongly focusedlight 650F2 that converges onto active device 760 on circuit board 740.In an example, light 650 can travel in the opposite direction fromelectronic device 706 to plug 10 in the case where active device 760 isa light-emitting device. Also in an example, the plug and receptacleinterfaced surfaces 403 and 713 are brought into contact at interfaceIF.

FIG. 8A and FIG. 8B are similar to FIG. 5A and FIG. 5B and illustrateanother example embodiment of plug endcap 400 where end wall interiorsurface 462 is planar and endcap front (outer) surface 403 is curved, sothat plug lens 500 is plano-convex, with the convex side on endcap frontend 402. Note that end wall interior surface 462 can also be curved indefining plug lens 500. This embodiment for plug lens 500 as describedis problematic in that endcap end 402 cannot provide a planar surfacewhen interfacing plug 10 with receptacle 700. Moreover, endcap front end402 now includes recesses 406 that can collect contaminants.

FIG. 9A is a cross-sectional view similar to FIG. 6 and shows plugferrule assembly 430 with the example plug endcap 400 of FIGS. 8A and8B. However, the plug ferrule assembly 430 further includes asubstantially transparent member 800 disposed at front end 402 of plugendcap 400. Substantially transparent member 800 has a front surface802, a rear surface 804 and an edge 806. Substantially transparentmember 800 provides the needed planar surface 802 that serves as theinterface surface when plug 10 engages receptacle 700. Substantiallytransparent member 800 also serves to protect recesses 406 fromcollecting contaminants by making plug lens 500 an internal lens, i.e.,the outer surface of plug lens 500 is not an outermost surface of plugferrule assembly 430. If necessary, substantially transparent member 800can include a curved or otherwise non-planar rear surface 804 so thatthe transparent place can serve as an additional lens element, e.g., aplano-convex or a plano-concave lens element. Substantially transparentmember 800 can be made of Polyetheremide (ULTEM®) or glass or sapphire.

In an example, front end 402 of plug endcap 400 is configured to supporta substantially transparent member 800. For example, endcap front end402 can include an annular lip 407 that allows for the substantiallytransparent member 800 to be supported at its edge 806. FIG. 9B is afront-on view of substantially transparent member 800 held by endcap 400at front end 402 using annular lip 407. FIG. 9C is a close-upcross-sectional view of endcap front end 402 showing how substantiallytransparent member 800 is held by annular lip 407.

FIG. 10A is similar to FIG. 9A and illustrates an example embodiment ofplug ferrule assembly 430 where plug lens 500′ comprises a GRIN lens850. GRIN lens 850 is supported by plug endcap 400 at front end 402.GRIN lens 850 includes front end 852 at endcap front end 402 and a rearend 854 at plug ferrule front end 402 so that it contacts or nearlycontacts bare optical fiber end 618. This allows guided light 650G inoptical fiber 602 to enter GRIN lens 850 at GRIN lens rear end 854 justas thus the light starts to diverge from bare optical fiber end 618 toform divergent light 650D. This divergent light bends as it travelsthrough GRIN lens 850 due to its gradient refractive index so that bythe time the light exits GRIN lens front end 852 at endcap front end 402it constitutes substantially collimated light 650C.

FIG. 10B is similar to FIG. 10A and illustrates an example embodimentwhere the GRIN lens 850 is incorporated directly into plug ferrule 200at a recess 209 at plug ferrule front end 202 so that no plug endcap isneed to support the GRIN lens. The plug ferrule 200 has a diameter DFand GRIN lens 850 has a diameter DL, wherein DL<DF.

FIG. 10C is a cut-away view of an example plug ferrule 200 that includesa GRIN lens at the plug ferrule end 202, with the plug ferrule operablyengaged with a light-transmitting member 710. FIG. 10D is similar toFIG. 10C, but with the plug ferrule 200 and light-transmitting member710 disengaged.

In an example, the GRIN lenses described herein may be of the typeformed by ionic diffusion into glass rods (i.e., an ionic-diffusionprocess), or may be of the type formed by drawing a pre-form so that ithas a select size and refractive index profile, and then forming GRINrods from the drawn pre-form (i.e., a fiber-drawing process). An examplepre-form is an optical fiber preform, such as one used to formgradient-index optical fibers.

Cylindrical Lens Embodiments

FIG. 11A is a top elevated view of a plug ferrule 200 shown operablyengaged to an example light-transmitting member 710 to form an examplefiber optic interface assembly 470, while FIG. 11B is a similar view butwith plug ferrule 200 shown disengaged from light-transmitting member710. FIG. 11C and FIG. 11D are cut-away views of the matedlight-transmitting member 710 and plug ferrule 200 of FIGS. 11A and 11B.Light-transmitting member 710 is as shown in FIG. 7D, and has a planarfront surface 713.

Plug ferrule 200 includes an internal cavity 270 having a front(forward) surface 272 and a rear (rearward) surface 274. Front surface272 includes a first cylindrical lens 276 with curvature (and thuspower) in the X-Z plane, while rear surface 274 includes a secondcylindrical lens 278 with curvature (and thus power) in the Y-Z plane.Thus, first and second cylindrical lenses 276 and 278 constitute a pairof crossed cylindrical lenses with powers in orthogonal directions.

FIG. 12A and FIG. 12B are close-up, cross-sectional views of plugferrule 200 and internal cavity 270, showing the bare optical fiber 616supported in plug ferrule bore 250. The cross-section of FIG. 12A istaken in the X-Z plane while the cross-section of FIG. 12B taken in theY-Z plane. The light path of light 650 is shown as dotted lines.

With reference to FIG. 12A, uniformly divergent light 650D from end 618of bare optical fiber 616 passes through second lens 278 without beingrefracted in the X-Z plane and reaches first cylindrical lens 276, whichrefracts divergent light 650F to form substantially collimated light650C in the X-Z plane. Likewise, with reference to FIG. 12B, diverginglight 650D in the Y-Z plan is refracted by second cylindrical lens 278to form substantially collimated light 650C that passes through firstcylindrical lens 276 without being refracted in the Y-Z plane. Theresult is a substantially collimated but astigmatic light beam 650C′,i.e., the light beam has a width in the X-Z plane that is greater thanthe width in the Y-Z plane. This astigmatic, substantially collimatedlight 650C′ passes through the interfaced planar front ends 202 and 712of plug ferrule 200 and light-transmitting member 710. This astigmaticsubstantially collimated light 650C′ then reflects from angled surface716 and proceeds to lens 750, which is has an anamorphic configurationthat receives astigmatic substantially collimated light 650C′ and formsfocused light 650F.

FIG. 13A is a top elevated view of an example plug ferrule 200 shownoperably engaged with light-transmitting member 710 to form an examplefiber optic interface assembly 470. FIG. 13B is a cut-away view of theengaged plug ferrule 200 and light-transmitting member 710, showing anexample configuration of the cross-cylindrical lenses 276 and 278 of theplug ferrule. Plug ferrule 200 is similar to that described above inconnection with FIGS. 11A through 12B, but includes another cavity 280adjacent cavity 270 and towards the plug ferrule rear end 204. The twocavities 270 and 280 are separated by a wall 281. Wall 281 includes theaforementioned rear surface 274 of cavity 270 and also includes anopposite surface 282 at the front of second cavity 280. Cavity 280 alsoincludes a rear wall 284.

In this cavity configuration, cylindrical lens 276 is now formed on rearsurface 274 of cavity 270 while cylindrical lens 278 is formed on frontsurface 282 of cavity 280. Thus, the two cylindrical lenses are part ofthe same wall 281 and can be thought of as constituting a single lenselement. The optical path of light 650 is essentially as that describedabove in connection with FIGS. 11A through 11D and FIGS. 12A and 12B,with light-transmitting member 710 having the aforementioned anamorphiclens 750 at input/output end 720 of light-transmitting member 710 toform focused light 650F.

Uses and Advantages

The optical interface devices, assemblies and components (e.g., plugferrules, light-transmitting member, etc.) disclosed herein have anumber of uses and advantages. By arranging the plug lens to be aninternal lens, and therefore by having the external surface of the plugto be a planar surface, the plug ferrule is less susceptible to theadverse effects of contaminants in the form of debris, liquids, etc.,because it can be more easily cleaned of contaminants.

In addition, by having the plug ferrule engage the correspondingreceptacle light-transmitting member by interfacing respective planarplug and receptacle surfaces, any contaminants that may find their wayinto the mating interface can be displaced upon mating the plug andreceptacle. This is particularly true of liquid contaminants, which aresubstantially dispelled by interfacing the plug and receptacle planarsurfaces. This is an advantage compared to plug and receptacle fiberoptic interface devices that use lenses where the external surfaces arecurved (i.e. not planar). This is because the presence of a liquidcontaminant between two optical surfaces of which at least one is curvedcan affect the refraction of light on that surface, thus modifying thefocal length of the lens and by that recuing the optical couplingefficiency. This is true even if the liquid contaminant is essentiallytransparent.

By contrast, the presence of a liquid contaminant between two opticalplanar surfaces does not substantially alter the refraction of light,and the only loss in coupling efficiency is caused by the opticalabsorption in the liquid contaminant. Such loss caused by opticalabsorption is anticipated to be acceptably low (typically less than 20%)for common water-based and oil-based contaminants. It is worth notingthat in some cases a liquid and substantially transparent contaminantpresent between two planar optical surfaces may even result in anincrease of optical coupling efficiency because the presence of thecontaminant can reduce or eliminate the Fresnel reflections, e.g., byserving as an index-matching material.

In an example embodiment, the planar-to-planar interface formed whenmating plug 10 and receptacle 700 can be spaced apart by a distance from0 mm (i.e., in contact) up to 100 microns. A slightly spaced apartconfiguration for the interface has the advantage that the interfacingsurfaces are less subject to being damaged by contaminants beingsqueezed between the confronting surfaces. Also, the planar surfacesdescribed have been shown as “vertical” surfaces, i.e., with thesurfaces at right angles to the central axes of the plug and receptacle.However, in other embodiments, the planar surfaces can have an angleother than 90 degrees relative to the respective central axes of theplug and receptacle. An advantage of bringing the planar surfaces intocontact at the planar-to-planar interface is that liquid contaminantscan be substantially expelled from the interface. This is referred toherein as a liquid-displacing interface.

An aspect of the disclosure includes a method of transmitting light 650through a liquid-displacing interface. The method includes supporting ina ferrule 200 of a ferrule assembly 430 an optical fiber 602 having anend 618. The ferrule supports a lens such as lens 500 or GRIN lens 850,operably arranged relative to the optical fiber end. The ferruleassembly 430 has a front end such as formed by endcap front end 402 orby substantially transparent member 800, and this front end defines afirst planar front surface. The first planar front surface may includeor otherwise be defined by, for example, endcap front surface 403,transparent member front surface 802 or GRIN lens front surface 852. Themethod also includes interfacing the first planar front surface with asecond planar front surface 713 of light-transmitting member 710 todefine the liquid-displacing interface. The method further includestransmitting the light 650 through the optical fiber, through the lensand through the liquid-displacing interface and to thelight-transmitting member.

In an example, the plug ferrule 200 defines a plug 10 having a smallform factor. With reference again to FIG. 4A, in an example, endcap 400has a diameter d that defines a dimension of plug 10. In an examplewherein plug 10 has a small form factor, d is between 2 mm and 4 mm.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present disclosurewithout departing from the spirit and scope of the disclosure. Thus, itis intended that the present disclosure cover the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A ferrule assembly for a first fiber opticinterface device for engaging a second fiber optic interface devicehaving a second planar surface comprising: a ferrule having a body, adiameter, a front end having a planar surface, a front section at thefront end, and a bore configured to support an optical waveguide, thebore having an end at the front section; a gradient-index (GRIN) lenssupported within the front section of the ferrule body and aligned withthe bore, the GRIN lens having a diameter, a front surface that definesa first planar surface that is co-planar with the planar surface of theferrule front end and a rear surface that resides immediately adjacentthe bore end; and wherein the GRIN lens diameter is less than theferrule diameter, and wherein the first and second planar surfacesdefine a liquid-displacing interface when the first and second fiberoptic interface devices are engaged.
 2. The ferrule assembly of claim 1,further comprising an optical waveguide supported in the bore, with theoptical waveguide having an end substantially at the bore end.
 3. Theferrule assembly of claim 1, wherein the GRIN lens is either anionic-diffused GRIN lens or a fiber-drawn GRIN lens.
 4. A first fiberoptic interface device, comprising: the ferrule assembly of claim 1; anda housing that operably supports the ferrule assembly.
 5. The firstfiber optic interface device of claim 4, further comprising an opticalfiber cable operably connected to the housing and containing an opticalfiber, with an end portion of the optical fiber supported by theferrule.
 6. The first fiber optic interface device of claim 4, furthercomprising: the second fiber optic interface device engaged with thefirst fiber optic interface device to define the liquid-displacinginterface.
 7. A ferrule assembly for a first fiber optic interfacedevice configured to operably engage a second fiber optic interfacedevice having a second planar surface, comprising: a ferrule having acylindrical body with a diameter and having a front section thatincludes a front end with a planar surface and a recess formed therein,the ferrule also including a longitudinal bore that runs down the centerof the ferrule body from the back end and terminates at the recess inthe front section; an optical fiber disposed within the bore, theoptical fiber having an end; and a gradient-index (GRIN) lens operablysupported in the ferrule body in the recess at the ferrule front end,the GRIN lens having a cylindrical shape with a diameter less than theferrule diameter and also having a first planar front surface that isco-planar with the planar surface of the ferrule front end and a rearsurface at or adjacent the optical fiber end, the first planar frontsurface and the second planar surface being parallel and defining aliquid-displacing interface when the first and second fiber opticinterface devices are operably engaged.
 8. The ferrule assembly of claim7, wherein the GRIN lens is configured to receive diverging light fromthe optical fiber end and form collimated light that exits the firstplanar front surface.
 9. The ferrule assembly of claim 7, wherein theoptical fiber end is in contact with the rear surface of the GRIN lens.10. A fiber optic interface assembly, comprising: the first fiber opticinterface device having the ferrule assembly of claim 7; the secondfiber optic interface device engaged with the first fiber opticinterface device such that the first planar front surface and the secondplanar surface define the liquid-displacing interface when the first andsecond fiber optic interface devices are operably engaged.